The present invention relates generally to a motor-driven compressor, and more particularly to a motor-driven compressor having an inverter for driving an electric motor.
The motor-driven compressor has an electric motor for driving a compression mechanism of the compressor and an inverter for controlling and driving the electric motor. The motor-driven compressor is often installed and used in a vehicle and has a problem of vibration developed by an internal combustion engine.
If any frequency spectrum of the vibration developed by the internal combustion engine encompasses the resonance frequency of the inverter substrate, the substrate resonates with the vibration of the internal combustion engine and the stress of a solder or the like on the substrate is increased. If the stress on the solder is increased, problems occur so that cracks are generated in the leads (or pins) which are connected to the substrate by the solder.
To prevent the above problems, a gel material is enclosed for damping or suppressing the vibration in a conventional inverter type motor-driven compressor. That is, an inverter chamber of the motor-driven compressor is filled with vibration-damping gel thereby to fix and seal the inverter and its elements. Thus, the inverter and the substrate are fixed, so that the vibration is restrained. The motor-driven compressor having such an inverter is disclosed in the Japanese Patent Application Publication No. 2003-322082.
However, the inverter whose chamber is filled with the gel is undetachably fixed. Therefore, the use of the vibration-damping gel is not suitable to a motor-driven compressor having such an inverter that needs to be removed as required.
Furthermore, since substantially the entire space of the inverter chamber should be filled with the gel, the inverter with such a chamber becomes heavier. Additionally, the need of high-temperature treatment for curing the gel requires large-sized equipment for raising the inverter chamber temperature, with the result that the production cost is increased and harmful load is inevitably applied to electronic components due to the high-temperature treatment.
The present invention is directed to a motor-driven compressor which is capable of reducing the vibration of an inverter substrate without filling inverter chamber with vibration-damping gel.